This invention relates to exterior pavements and in more particular to exterior architectural pavements or paving systems which are decorative as well as functional.
Architectural exterior pavements or paving systems are, generally speaking, those which are intended to present a pleasing and/or decorative visible surface. Architectural pavements are expected to carry pedestrian traffic and light vehicular traffic and, on occasion, have to support heavier vehicular traffic as well as endure or survive other forces ranging from freezing and thawing to earthquakes and tremors. Examples of such pavements have been used as walkways, courtyards, malls, streets, gardens, patios and/or the wearing or decorative surfaces of a building roof or deck. The decorative appearance of known architectural pavement is provided by the topmost layer of paving elements (hereinafter, pavers) which are usually rectangular or polygonal blocks such as clay tile, concrete, slate, stone, impregnated wood or other materials that provide a decorative but sturdy wearing surface and can be arranged in a decorative or aesthetically pleasing pattern.
Pavers are usually supported at the bottom by, variously, a sub-base of natural earth or compacted earth, a base which usually rests upon a sub-base and may be either rigid or somewhat yielding compared with the sub-base, and a setting bed laid on the base and supporting the pavers. A base usually comprises compacted stone or gravel, or compacted sand or compacted sand and gravel, asphalt, concrete, prior pavement or the load bearing aspect of a roof deck.
Two prior methods have been commonly employed for laying pavers on a base. The first is to lay desirably thin pavers and a setting bed on a rigid base, such as reinforced concrete, and then grout the joints between pavers so that the entire system is rigid. Problems with this arrangement arise, however, due to forces exerted from above, such as heavy vehicles, or exerted vertically from below as by sub-base instability, quakes or tremors, or horizontally by movement due to thermal or moisture expansion and contraction, which tends to cause the pavers, setting bed and/or the base to crack at random and monolithically.
A second procedure requires the use of relatively thick pavers (1-1/4 to about 4-1/2 inches thick) which are placed on or laid on a bed or base of sand, asphalt or the like which permits each individual paver to "float". Movement will then occur between pavers rather than through them. This method, however, requires the use of relatively thick pavers which have the necessary strength to prevent breaking under foot, under vehicular loading or other adverse forces mentioned above. Thick paver systems are, however, relatively expensive compared with so-called "thin" systems which employ pavers from about 1/8 inch thick for metal and from about 3/8 inch thick for other strong pavers, to about 1-1/4 inches thick for weak pavers made of asphalt or limestone, for example. With such prior thin pavers, setting beds of slightly less than one inch to about two inches in thickness have been employed. Thick paver systems offer no decorative advantage over thin paver systems.